researchers at texas a&m university (college station, texas) have developed a novel chameleon-like, phase-change material by adding tungsten to vanadium oxide that they believe could provide for more powerful computers than the current silicon-based technology.
researchers are exploring vanadium oxide as a material for future computers. (texas a&m university)
according to a report on the university website, the material switches from being an insulator to a conductor depending on the heat or voltage applied. the addition of tungsten allows for better control of the phase-change transition.
“among other things, the researchers showed that tungsten allows the transition to occur over two very different pathways,” the report explained. “the result is that the transition from insulator to conductor happens easily and quickly, while the transition from conductor back to insulator is more difficult.”
a researcher described it as one process taking place on a superhighway but returning on back roads, which “could be exploited in future computers.” scientists use the tungsten to tune the temperatures where the phase change takes place.
the research was recently published in chemistry of materials. the abstract read:
“materials exhibiting pronounced metal–insulator transitions such as vo2 have acquired great importance as potential computing vectors and electromagnetic cloaking elements given the large accompanying reversible modulation of properties such as electrical conductance and optical transmittance. as a first-order phase transition, considerable phase coexistence and hysteresis is typically observed between the heating insulator → metal and cooling metal → insulator transformations of vo2.
“here, we illustrate that substitutional incorporation of tungsten greatly modifies the hysteresis of vo2, both increasing the hysteresis as well as introducing a distinctive kinetic asymmetry wherein the heating symmetry-raising transition is observed to happen much faster as compared to the cooling symmetry-lowering transition, which shows a pronounced rate dependence of the transition temperature.
“this observed kinetic asymmetry upon tungsten doping is attributed to the introduction of phase boundaries resulting from stabilization of nanoscopic m2domains at the interface of the monoclinic m1 and tetragonal phases. in contrast, the reverse cooling transition is mediated by point defects, giving rise to a pronounced size dependence of the hysteresis.
“mechanistic elucidation of the influence of dopant incorporation on hysteresis provides a means to rationally modulate the hysteretic width and kinetic asymmetry, suggesting a remarkable programmable means of altering hysteretic widths of an electronic phase transition.”
|